Improved vaccine design and delivery as part of an integrated approach to meet the public health challenge of typhoid fever in developing countries

Salmonella enterica serovar Typhi (S. typhi) is a significant cause of typhoid fever in humans. Gastrointestinal infections with this and the closely related bacterium S. paratyphi that causes paratyphoid fever pose a public health challenge, particularly in developing countries where people of all age groups are commonly affected. However, limited data exist to estimate the total clinical burden of such enteric fever in Asian and African countries. Despite the demonstrated success of a number of typhoid vaccines, these are still not deployed widely enough to protect whole communities. In typhoid fever-endemic areas especially there is a pressing need to consider the introduction into routine public health programs of new generation typhoid vaccines. To this end, several novel conjugate vaccines have undergone clinical trials for human use. The optimum age at which children are immunized needs to be re-evaluated as there is a requirement for an efficacious and potent vaccine that can be used in children below the current vaccination window of two to five years of age. This review highlights the key virulence factors of S. typhi that are associated with antibiotic resistance and considers the need to introduce widespread public vaccination programs to help combat typhoid fever worldwide. Improvement in sanitation and water systems is the principal long-term solution to disease prevention. In addition, early diagnosis and appropriate treatment can reduce rates of morbidity and lessen disease severity in individual patients, even in regions with restricted health care facilities. In order to support national vaccination programs, in locations where typhoid fever is endemic a range of policies on public health education, good hygiene practices, increased quality of the supply of drinking water and regular monitoring of S. typhi antibiotic resistance patterns should be instigated.